1. Field of the Invention
The invention relates to an article for controlled and substantially uniform release of a volatile organic substance into the surrounding atmosphere. The volatile substance can be in particular a fragrance, an insecticide or an insect repellent.
2. Description of the Prior Art
Silicone elastomers are permeable to gases and liquids. Studies of diffusion of fragrance across a silicone wall are abundant, while studies of diffusion across a silicone matrix are fewer in number. Japanese patent No. 82-40 558 describes a method of manufacturing a silicone elastomer matrix for diffusing fragrance into the atmosphere. The silicone elastomer composition is mixed with the fragrance and, after adding an organometallic salt, curing of the composition is then initiated in a mold. The matrix obtained has a nonlinear diffusion of the fragrance due to an incompatibility between the polymer and the fragrancing composition.
U.S. Pat. No. 4,703,070 shows the importance of incorporating a compatibilizer in order to avoid exudation of the fragrance over time. It describes a method of manufacturing a matrix consisting of a silicone elastomer, a compatibilizer and a fragrance. However, this matrix does not give a linear diffusion of a composition which is constant over time and for temperatures ranging from 15xc2x0 C. to 60xc2x0 C.
There is thus a need for an article allowing controlled and substantially uniform release of a volatile organic substance such as a fragrancing composition, an insecticidal composition or an insect-repellent composition, over a broad range of working temperatures.
The invention has for purpose to satisfy this need.
The invention relates more particularly to an article for controlled and substantially uniform release of a volatile active organic substance into the surrounding atmosphere, the article including a silicone elastomer matrix (a) of desired shape in which are dispersed the volatile substance (b) and an effective amount of an agent (c) for compatibilizing the volatile substance and the silicone elastomer of the matrix, wherein the compatibilizer (c) is an organic solvent with a Hildebrandt solubility parameter from 8 (cal/cm3)xc2xd to 14 (cal/cm3)xc2xd and a vapor pressure from 0.0005 mm to 0.8 mm of mercury (0.06 Pa to 105 Pa) at 20xc2x0 C.
According to one specific embodiment the volatile organic substance is a fragrance or a fragrancing composition.
According to another preferred embodiment at least one of the following optional additional constituents is dispersed in the matrix:
an emulsifier (d) in a proportion which is effective in avoiding sweating or exudation of the volatile substance (b) from the matrix (a) during storage of the article, and
a silicone fluid (e) in a proportion which is effective in facilitating release of the volatile substance (b) at temperatures from 35xc2x0 C. to 60xc2x0 C.